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Neanderthal Genome Sequenced

Researchers have produced the first whole-genome sequence of the Neanderthal genome. The analysis provides the first genome-wide look at the similarities and differences of the closest evolutionary relative to humans.

Neanderthals, Homo neanderthalensis, are the most recent extinct relative of modern humans. The fossil record suggests that they diverged from the primate line that led to present-day humans, Homo sapiens, about 400,000 years ago in Africa. Neanderthals migrated north into Eurasia, where they became geographically isolated and evolved independently from the line that became modern humans in Africa. Neanderthals lived in Europe and western Asia, as far east as southern Siberia and as far south as the Middle East. Approximately 30,000 years ago, they disappeared.

A research team led by Dr. Svante Pääbo at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, extracted DNA from the bones of 3 female Neanderthals who lived some 40,000 years ago in Europe. The bones were discovered at Vindija Cave in Croatia. An international research team, including scientists from NIH’s National Human Genome Research Institute (NHGRI), compared the Neanderthal DNA to samples from 5 present-day humans from China, France, Papua New Guinea, southern Africa and western Africa, as well as to chimpanzee DNA.

The analysis, which appeared in the May 7, 2010, issue of Science, shows that Neanderthal DNA is 99.7% identical to present-day human DNA and 98.8% identical to chimpanzee DNA. Present-day human DNA is also 98.8% identical to chimpanzee. The comparison produced a catalog of genetic differences that allowed the researchers to identify features unique to present-day humans. Many regions of the Neanderthal genome, they found, are more like those of the chimpanzee than present-day humans.

"The genomic calculations showed good correlation with the fossil record," says coauthor Dr. Jim Mullikin, acting director of the NIH Intramural Sequencing Center. "According to our results, the ancestors of Neanderthals and modern humans went their separate ways about 400,000 years ago."

The analysis suggests that up to 2% of the DNA in the genome of present-day people outside of Africa originated in Neanderthals or their ancestors. Neanderthals appear to have re-encountered anatomically modern humans in the Fertile Crescent of the Middle East about 60,000 years ago. As modern humans migrated out of the Middle East and dispersed across the globe, they carried Neanderthal DNA with them.

While the team didn't find traces of Neanderthal DNA in the 2 people from Africa, a more systematic sampling of African populations may reveal Neanderthal DNA in some indigenous Africans as well. "These are preliminary data based on a very limited number of samples, so it is not clear how widely applicable these findings are to all populations," says Dr. Vence L. Bonham of NHGRI.

"You must appreciate that this international team has produced a draft sequence of a genome that existed 400 centuries ago," says NHGRI Director Dr. Eric D. Green. "Their analysis shows the power of comparative genomics and brings new insights to our understanding of human evolution."